Conventionally, there has been known a white light Source using a light-emitting diode (LED). The white light source using the LED is such that a phosphor layer is formed on a light emitting surface of an LED chip by mixing a phosphor and a transparent resin, and the color emitted by the LED chip and the color emitted by the phosphor are combined to produce white light. For example, Japanese Patent No. 3509665 (Patent Document 1) discloses a white light source combining a blue LED having an emission peak at 420 to 490 nm and a yellow phosphor. However, there is a problem that the white light obtained from the white light source has high intensity, but is pseudo white with a slight yellow tint and has poor color reproducibility.
As a white light source with improved color reproducibility, for example, Japanese Patent Laid-Open No. 2007-96133 (Patent Document 2) has recently proposed a white light source combining an ultraviolet light-emitting diode having an emission peak at 370 to 410 nm and a phosphor layer containing a blue phosphor, a green phosphor, and a red phosphor. According to the white light source, color reproducibility is improved and pure white light is obtained by using a blue phosphor, a green phosphor, and a red phosphor.
Patent Document 1: Japanese Patent No. 3509665
Patent Document 2: Japanese Patent Laid-Open No. 2007-96133